[clang] [clang-tools-extra] [lldb] [clang] implement CWG1980 and CWG2064: instantiation-dependency improvements (PR #190495)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

ping, this has been sitting for two weeks.

Any objections we merge this and continue on post-commit?

https://github.com/llvm/llvm-project/pull/190495